Anglerfish islet tissue will be perifused in an vitro system in order to determine the phasic release patterns of fish islet hormones in response to various secretagogues of known activity in mammalian systems. Following perifusions in the presence of low glucose, agents such as elevated glucose, other sugars, adenylate cyclase-phosphodiesterase agents, amino acids, proteins, and neurogenic agents will be added; release of hormones will be measured by specific insulin, glucagon, and somatostatin (SRIF) radioimmunoassays. Studies on the biosynthesis of somatostatin (SRIF) will be continued. We have evidence that SRIF, with immunologic, biologic, and molecular size characteristics similar to ovine hypothalamic SRIF is synthesized by anglerfish islet tissue in vitro. Further studies will be aimed at identifying and isolating a biosynthetic precursor of SRIF, which we believe is present in anglerfish islet tissue. Further purification and characterization of islet subcellular fractions will be pursued in an attempt to localize the sites of enzymatic cleavage of prohormones to hormones in anglerfish islet cells.